As core to Facebook as News Feed and Timeline, Graph Search is now rolling out to hundreds of millions of users in the U.S., bringing with it the promise of uncharted exploration and the potential for substantial advertising dollars.

First unveiled in January, Graph Search is a social-network search engine that ingests natural language queries on people, places, and things and spits out results previously hidden inside Facebook's world. The engine, referred to as a "third pillar" product by the company, finally gives people a way to surf through forgotten memories or locate shared moments with friends.

Really, though, Graph Search is less about helping you uncover old photos and more about taking you down a rabbit hole of discovery where your quest to know more about someone or something is never quite satisfied, and everything you find inspires you to go deeper into this underground world where people are intertwined by their connections, interests, photos, and adventures.

Despite speed and language comprehension improvements, this new dimension is still far too difficult to navigate, potentially very unsettling, and not yet available on mobile, where Facebook users are spending more of their time. Facebook has its work cut out for it if Graph Search is going to be a commercial hit that lives up to Wall Street's expectations.

Here's what Facebook needs to get right:

Make it intuitive

When you think of Facebook Graph Search you should imagine the endless types of queries you can perform. It's as if the social network has made available to you everything your curious and twisted self could ever want to know.

Forget scanning your crush's or ex's Timeline to indulge your crazy -- his or her Facebook relationships and activities are available for deeper dissecting with a little Graph Search know-how. Try a "friends of [crush] who live in [his/her city]" query or a "photos of [crush] in [his/her city]" query if you want a closer peek at this person's life. Both seemingly harmless searches can, depending on friends of friends' privacy settings, provide an interesting window into the life of your object of affection. It's a view you may not really want to see, but one you probably can't help yourself from taking -- once you know the option is there.

Graph Search as a stalker's paradise, innocent or otherwise, is one of the more compelling use cases of the search engine, at least in terms of upping member engagement, as it has the potential to keep people glued to the social network for hours as they investigate their way through little clues or torture themselves trying to find photographic evidence of liaisons. Though these self-indulgent options exist, Facebook does a lousy job at exposing the capabilities of its search engine to the average person. Newbies get a little tutorial that introduce them to the omni-search bar, but the crash course is generic and will be forgotten in a few days or weeks.

In my own experiences with Graph Search, I defaulted back to basic searches for people and Pages after just a few weeks, simply because the search engine forces you to think too much about what you want to find. Query suggestions have improved with the wider release, meaning that Facebook should be better at guessing what you want as you type. The search bar itself is also now more instructive with a prompt that reads: "Search for people, places, and things."

Still, Graph Search is not as obvious or intuitive as it should be. This is a problem. Graph Search will flop as a pillar product that engages users and generates revenue if the company doesn't make its unique advantages plainly apparent to the average Facebook user.

Facebook needs to make you safe

There's something unsettling about Facebook making an unexpected connection between you and something you've shown interest in, and then highlighting that behavior to an undefined group of people. "Friends of my friends who like weed," is one telling query where you can find potheads in your extended network who probably don't realize their extracurricular preferences are on display to strangers.

Sure, Graph Search obeys the privacy settings of your posts and Facebook encourages you to view and adjust what groups of people can see your stuff, but those measures won't prevent embarrassing revelations from surfacing.

Graph Search could act like a wake-up call that encourages people to pay more attention to their privacy settings, cut back on their likes or updates, or leave Facebook altogether. History tells us that a mass exodus won't happen, but there's plenty of evidence to suggest that member attention, especially the attention of tweens and teens, is shifting to other, more private applications, in part because of a fear of being held accountable for incriminating posts or photos.

Graph Search will only exacerbate this concern of being overexposed, so Facebook needs to figure out a way to ameliorate fears and make people feel safe, especially since the situation will become infinitely stickier once Graph Search is capable of surfacing old status updates.

Ads that make sense

For Facebook and its investors, Graph Search's greatest hope is to bring in substantial advertising dollars, perhaps on the scale of Google's search ad business. That hope, reflected in a small Monday gain for Facebook's otherwise sagging shares, is far from being realized.

While Wedbush analyst Michael Pachter initially pegged revenue from the curated search tool at between $3 billion and $4 billion by 2015, Facebook has set revenue expectations extremely low. "I do want to temper near-term expectations a little bit on revenue coming from other areas like Gifts or Graph Search," CEO Mark Zuckerberg told investors and analysts in January.

Thus far, the company has only tested page-two advertising placements on Graph Search results pages, and the ads are not targeted to a person's queries, which makes them generic space-fillers. It also seems that sponsored results, a model Google employs, may not work with Facebook's search engine.

But by helping people locate nearby vegan restaurants or bars their friends like, Facebook is in a position to connect local businesses on the platform with would-be customers and capitalize on the local search market, an area dominated by Yelp. The company has partially laid a foundation for this by remodeling mobile Pages to highlight essential business information such as location and contact info.

Whatever revenue-generating tactic Facebook eventually tacks on to Graph Search, the company will need to be extra-sensitive given the personal nature of search results. Facebook hasn't always shown attention to detail when it comes to advertising. Recently, the company decided to remove ads appearing alongside controversial content on Pages and in groups after some advertisers threatened to suspend their advertising campaigns.

This puts Facebook in the tricky spot of needing to appease Wall Street with monetizing Graph Search while not alienating users or advertisers.